4-Aminoindoles as 1,4-bisnucleophiles for diversity-oriented synthesis of tricyclic indoles bearing 3,4-fused seven-membered rings

A straightforward access to tricyclic indoles bearing 3,4-fused seven-membered rings has been established by using 4-aminoindoles as 1,4-bisnucleophiles in three-component reactions. 1H-Azepino[4,3,2-cd]indoles, 4,6-dihydro-1H-azepino[4,3,2-cd]indoles and 1,3,4,6-tetrahydro-5H-azepino[4,3,2-cd]indol-5-ones could thus be synthesized in one pot in moderate to good yields. Beyond opening access to 3,4-fused tricyclic indoles, the use of easily accessible 4-aminoindoles as C,N-1,4-bisnucleophiles also provides a new platform to be used in a diversity-oriented synthesis strategy, fully displaying its benefits of maximizing molecular complexity and reaction diversity.